On Friday, @CDCgov updated its guidance to say the coronavirus is airborne.

On Monday, it went back to the previous guidance, which emphasizes droplets and distancing. What happened? 1/x https://www.nytimes.com/2020/09/21/health/coronavirus-cdc-aerosols.html

My sources –- official and not -- tell me that this time, it wasn’t political meddling, but rather an error. The document was posted before it was ready. But this error has enormous implications nonetheless for the agency's credibility. 2/x

But first, what do we make of this aerosol thing?

Some aerosol experts said this is the CDC acknowledging that aerosols are the primary driver. But that’s not how I read it, nor did many experts I talked to. 3/x

They saw it as the CDC saying droplets *and* aerosols are important, and inhalation is the primary (rather than touch).

Also, does it really matter? Ultimately what matters is how people protect themselves. 4/x

And how is that? Ventilation matters. 6 feet indoors may not be enough. Wear masks. Etc. The same stuff we have been talking about. 5/x

One other thing missed by many: the revision said: “Airborne viruses, including COVID-19, are among the most contagious and easily spread.” That is a HUGE deal for hospitals. 6/x

As @SaskiaPopescu noted, for a virus that's truly "airborne” you need N95s for health care workers all the time, and you need negative pressure rooms for everyone. 7/x

More importantly, this is only the latest of missteps from the CDC. Whether because of political interference or their own mistakes, the world’s premiere public health agency, during the biggest public health crisis of our lifetimes, keeps reversing itself. 8/x

As @CarlosdelRio7, normally one of the agency’s staunchest supporters, said: “It’s not something that instills a lot of confidence.”

thanks to him, @AbraarKaran @linseymarr and @SaskiaPopescu 9/9